Resistance unit



y 1932. N. J. CONRAD RESISTANCE UNIT Filed Jan. 30, 1928 2 Sheets-sheaf. 1

QifiZ/Grifi' Nzc/iplas \Z Conrad May 17, 1932. v CONRAD 1,858,483

RESISTANCE UNIT Filed Jan. 50, 1928 '2 Sheets-Sheet 2 33 4 46 ZQQ 6 V 4? 6 sarily be connected l' m ma May 17, 1932 UNITED STATES PATENT oluucs mcnoms J. com, or W'ILIETTE, rumors, Ass'renon, BY amen-n Assume.

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stoodthat the invention is not to-be may be employed wherever.

to such use, but found suitable.

As explainedin my co-pending application,. Serial' No. 244,015, filed December 31, 1927, potential transformers which are applied to the synchronizing, indicating and recording of .alternatin current, must necesto the main buses. In this location then failure-would hazard the buses and generating or transformer equipment'unless reliable protection is Whereas, it. is customary to put 1 fan afuse in the circuit of such potential transformersto interrupt any excessive flow of current, it has been found highly advisable to inserta protective resistance in addition to the fuse in series with such potential trans.

gsformers tolimit' the possible flow of current upon a short circuit at or ne'arthe primary terminals of the transformer. The use of such a resistance limits the short circuit cur'-' rent without appreciably disturbing-the accuracy of the potential transformer as a part of an indicating circuit. That to say, in

the preferred form-of my invention, the 5 cycle is practicallythe same as the resistance. The primary; voltage drop is j lefss than two volts on 6600 to 132000 volts" '0 the potential transformer is carrying a load of 200 volt a rnperes. Therefore the efiect of this resistor onmeter 'le.'-

potential. transformer installation when\ may be inspected without removin it from I This. embodiment ofthe invention also permits the mounting of the resistor in standard mountings such as are now emplayed for fuses, so that the problem of satis- 5 factorily mounting the resistor is solved by adequate means now at hand. t

In order to acquaint those skilled-in the art with the manner of constructing and:opcrating a device embodying my invention, I- co shall'describe the same in connection with. the accompanying drawings, in' which a specific embodiment disclosed. In the-drawings r Fig. 1.is a side elevational view of a resister embodying my invention;

Fig. 2 is'a top plan view of the same; Fig. 3is a bottom plan view of the same; Fig. 4 is a longitudinal cross section parallel to the plane of the pa r in Fig. 1'; Fig. 5 is an end view wit the cap or cover removed showing one terminal connection;

Fig. 6 is a fragmentary longitudinal view of a modification showing the manner in which a series of resistance units may be 7 mounted in the same container; Fig.7 is a transverse cross-sectional view taken on the line.7 7 of Fig. 6;

Figs 8 is -a longitudinal Section like that in Fig. 4, showing a modified form of the invention;

Fig. 9 is an end view, and Fig. 10 a side view, of a detail element; for inakm connection be'ween the wire resistance an 'th'e-terminal and for supporting the end of the porcelain sleeve; and

Fig. 11 -is alongitudinal cross section through a modified form-of rmistance unit adapted for carryinga largercurrent'flowj and presenting a lower resistance.

As shown in Fig. 1, the resistance'uni-t of I my invention comprises aglass sleeve 1 upon one end of which there is cemented the cap ferrule 2 comprising a brass cup-shaped element of exterior cylindrical form having its 5 sides slabbed off as indicated at 3--3 in Fig.

3. The opposite end of the sleeve has a sleeve ferrule 4 which has a part of the sides slabbed off, as indicated at 5-'-5 in Fig.2, to

provide the shoulders 6-6.

I the open market as the S & C fuse; In

fact, in external construction the resistance unit is substantially identical with the well known S & G fuse and is adapted to be mounted in the same mountin which will support and connect the said & C fuse.

' 1e sleeve 1 is cemented to the ferrules 2 and 4 by a fusible metal indicated at 7-7, to provide a gas tight seal. Obviously, other materials may be used to secure this result of securing the brass ferrules upon the ends of the glass sleeve.

The upper ferrule 4 has a thickened wall indicated at 8 in Fig. 4 providin a conical shoulder 9 flaring outwardly, an .an annular recess 10 defined by the flange portion 11.

The end of the upper ferrule 4 is closed by a sealing disc 12 which has a central arched or outwardly bulged portion and a flat radial portion 13 and a cylindrical flange 14 embracing the inner surface of the flange 11 and lying in the annular recess 10. This closure or plug 12 is preferably made of sheet metal and it maybe pressed into place after the other parts, hereafter to be described, are inserted in the housing which is formed by the glass tube and the attached ferrule.

A body of insulating material, in the present c'ase wet process porcelain, 15 in the shape of a hollow rod having a helical groove on .the outside of the same is disposed within the glass sleeve 1. At its ends the hollow rod or tube has transverse openings 16 at one side of the bore 17 in the hollow rod 15, and

larger transverse openings 18 on the opposite side of the bore 17 and in alignment with said openings 16. j

The core 15 is. provided with metallic mounts, in this case comprising short rods 19'-19', of cylindrical form slabbed oil at their sides for a short length to provide a flat seating surface for the heads of the terminal screws 20--21 which are threaded through themounts 1919. These rods 19--19-extend out of the end of the bore 17 and theouterends are threaded. The rod 19 at the inner end of the core 15 is threaded into a threaded boss 23 formed on the inside of the bottom of the cap ferrule 2.

A wire resistor comprising a helical coil of nickel chromium reslstance wire is wound about the core 15 being disposed in the grooves 24 thereupon, and the ends of the wire are fastened under the heads of the 'screws 20 and 21, whereby the mounts 19-19 become not only the mechanical support for the core 15, but electrical terminals for 'the resistbr 25.

The resistor 25 is, in the present instance,

' a relatively small size wire wound in the mounting s form of athelical coil of small diameter, like a coiled spring, and then the coil is wound in the grooves 24 on the core 15, the groove 24 bemg a continuous helical groove.

Threading of the mount 19 at the right of Fi 4 in the boss 23 in the cap 2 connects the ad acent end of the resistor with the cap ferrule 2 for external connection. The mount 19 at the opposite end extends through a 1 er 26, which, in this case, comprises mere y a strip or flat bar having the ends 27 thereof turned up 9 and secured to the b0 as b means of the machine screws 2828.

T e said spider 26 has a hole at the center loosely embracing the aforesaid mount 19.

If desired, the bar 26 may be threaded upon the threaded end of the rod mounts 19. I depend upon electrical connection between the mounts 19 and the ferrule 4 to be made by a flexible metallic braid 30, through the central part of which a machine screw 31 is passed and threaded into the end of the rod mount 19. A washer 32 lies under the braid ,30 to prevent cutting of the same against the end of the rod 19.

The ends of the braid 30 are connected to the slopin shoulder 9 by small machine screws 33. ow it will be seen that by the loose mounting of the mounting rod 19 in the spider 26, the expansion and contraction of the core, due to heating and cooling, is free The device is mounted in spring jaws of to fit the shoulder y ofthe ferrule 4 the character disclosed in my Patent No. 1

1,665,446 dated April 10, 1928-withthe shoul der 6 bearing agalnst the jaws to support the weight of the device in the mounting; The unit is prevented from dropping out of the mounting or being accidentally displaced from the same by wire bails which overhang the ends of the spring jaws.

The device illustrated in Figs. 1m 4, when made for use in connection with a potentlal transformer on 7500 volts, has a resistance a of 45 ohmsand is intended to be connected in series with a fuse having a rating of ampere, In that case the entire length of the device is approximately 13 inches, the resistor comprisirlrg No. 20 rown & Sharpe gage nichrome o. 4 wire, approximately 5 feet in length wound first on a nd inch arbor, and then wound on the core15, which is ap roximately 1 inch in diameter.

ere a greater length of resistance wireis employed, as for example on 37000 volts, the glass sleeve 1 is necessarily longer and the resistor should be longer. In that event, two cores with resistors thereupon are connected together in series within the sleeve 1, as indipins 38, in this case three in number, extending radially outwardly into contact with the walls of the glass tubing 1 to support the compound resistor at the joint, which is approximately at the center of the sleeve 1.

These pins 38 lie in radial holes which are intersected by threaded openings 39.extending longitudinally of the block 37 with small pointed set screws 40 adapted to engage the inner ends of the pins 38 for holding the same Y in extended position to-minimize the play which the block .37 may have with respect to the sleeve 1. The pins 38 are projected outwardly so that they fit substantially snugly the inside of the tube 1,.t0 prevent any lost motion at this point which would permit the resistor or the core 15 to come in contact with the glass, or allow rattling of the device to insulating rod 43 are formed in the shape of caps 44 and 45. These caps are identical in construction and comprise flanges overhanging grooves 46 and 47 in the ends of the porcelain rod 43. A series of three set screws 48 in the cap 44, and 49 in the cap 45, are projected inwardly into the grooves 46 and 47, respectively, to hold the mounting caps on the ends of the hollow rod 43.

The caps have threaded studs 50 and 51 extending axially therefrom. is threaded into a collar 52 which, in turn, is

threaded into the threaded boss 53 in-the inside bottom wall of the cap'ferrule 2. The mounting member 45 has a. terminal screw 54 which receives under its head the end of the wire resistor 25, and which has its shank extending into an opening 55 formed in the hollow rod 43 in thebottom of the groove 47. v The extension of theshank of the screw 54 into said opening '55 prevents the mount-' ing member 45 from turning on the rod 43.

In like manner, the front end of the resistor wire 25 is clamped under the end of the terminal screw 56, which has its shank projected into the opening 57 in the bottom of the groove 46 to prevent the mounting member 44 from turning on the hollow rod 43.

The axially. extending boss 50 on the mounting member 44 projects loosely through a hole in-the cross bar or spider 26, the construction of which is similar to that shown The stud 51' in connection with Figs. 1 to 5, inclusive. In

.able screws like the screws '28 shown in Fig.

5. In a similar manner, electrically, the boss 50 is connected to the sleeve ferrule 4 by means of a flexible metallicribbon 30, the

ends of which are mounted on the shoulder 58 by means of the screws 33.

The cap member 12 and its manner of closing the end of the sleeve ferrule 4 at the to of the unit is as described in connection with the device of Figs. 1 to 5.

The braid or ribbon 30 is likewise fastened to the hub 50by a screw 31 and washer 32.

The form of'mounting shown in Figs, 8 to 10, inclusive, is applicable to all forms in which the resistor wire is of relatively small diameter, that is, is fine wire.

In Fig. 111 have shown a resistance unit of relatively large current carrying capacity and relatively small resistance, for example, of 5 amperes maximum capacity and 2 ohms resistance. I

In this construction, the glass sleeve 1 and the metallic ferrules 2 and 4'with their immediately connected parts are identical with the structure shown in Figs. 1 to 5, inclusive. The porcelain core or rod 60 has a helical groove for receiving the ribbon resistor 61, which, in the present case, is of the order of th inch wide and approximately .045 in. thick nichrome wire *wound in a straight heli cal coil of approximately Z ths inch inside diameter.

The procelain core 60 has plain cylindrical ends with transverse openings therethrough for receiving the threaded terminal plugs 62 and '63 which pass looselythrough the openings in the core, but are threaded into transverse openings in the short mounting rods 64 and 65.

The plugs 62, and .63 are drilled and tapped throughout the major part of their length to receive the set screws or binding screws 66 and 67. Transverse openings or bores 68 and 69 are formed through the remote ends of the screw plugs 62 and the ends of the resistorare projected through said openings 68 and 69 and are gripped therein by the binding screws 66 and 67 to form a firm sistor from uncoiling and making electrical connection with the mounting rods 64 and which. are substantially like. the mounting rods 19 shown in Fig. 4. p

The rod 65 is threaded into thehollow boss 13, the inside of the cap ferrule 2, and the rod 64 is passed loosely through the spider 26, which has its ends 27 fastened by machine screws 28, as shown in 5, to the sloping shoulder 9.

The'end of he mounting rod 64'is connected to 'a flexible braid connection 30, as described in connection with Figs. 4 and 5.

The closure cap 12 hermetically seals the end.

of the ferrule 8 and closes the unit.

vIn each construction, the resistor is enclosed in a hermetically sealed'weather ti ht casing, one end being anchored to one errule and the other end being permitted to have endwise pla for expansion and contraction with a exibleconnecting lead or terminal 'oining the said free end of'the resistor wit the other ferrule.

The outside casing, that is, the glggss sleeve and terminals and caps, being su antially identical with the well known. form of sleeve above referred to, requires no additional part to be carried instock for said casing.

The resistor be held out of contact with the glass sleeve an spaced therefrom by an airspace, does not subject the glass, even when the resistor is heated, to any injurious streses.

- inherent resistance c arenot affected by heating, and the resistor If desired, the casing may be filled with insulating filling, such as a liquid dielectric, but I do not generall employ the same. The

llaracteristics of the unit does not deteriorate with age or service.

I do not intend to be lim ted'to the precise details shown or I claim: I

- l 1. A resistance unit comprising an insulat- I ing sleeve having 'a cap secured upon one end thereof, a ferrule secured on the other end, a central rod of insulation, metallic mounts for the ends of the rod, one of said mounts being secured to the cap, a; spider connecting I the other mount inside the ferrule, a wire re:

sister disposed on the rod and connected to said mounts, and a closure for'the end of the ferrule.

'- another terminal electrically and suppo mounts, an I enclosing casi-n' contraction of the rod.

radially to permit 'endwise expansion and 3. In combination, a rod of insulation, 1a

resistor wound "on the same, metallic mounts ha f studs extending from the ends of the rod, said mounts being non-rotatably secured to the rod, an enclosing sleeve of insulation having a cap ferrule at one end and A havingiajthre aded socket. for receiving one of said studs, a 'sleeve ferrule on the other end of the sleeve, a spider in said-latter ferrule'supporting other stud radially, 2..

flexible lead connecting the said stud and said sleeve ferrule, and a closure for the end'of the sleeve ferrule. v

' 4. In combination, a hollow rod of insulating material having a wire resistor wound thereupon, short metallic mounting rods lying looselyin the ends of the bore of the hollow rod, the ends of the hollow rod having diametrical openings therethro h, and ter- I minal screws threaded into sai mountin rods and lying in said diametrical bores, sai

terminal screws lying loosely in said diametrical openings'and connecting the ends of the wire resistor to said mounting'rods.

5. A resistance unit comprising a central core of insulation, an electric resistor su ported thereby, said core having a longitu i'- nal bore at ea'ch'end, short conducting rods inserted one in each bore, means for revent ing the withdrawal of the rods, sai means permitting a limited amount of free movementbetween at least one of the rods and the.

core, an electrical connection between therods and the respective ends of the resistor, a sleeve of insulating material around the resistance unit, and metallic ferrules'closing the end of the sleeve, one of saidv bei threaded into and supported by one of said ferrules. v

. 6. An electric apparatus com risin an enclosing'tube, an insulating co e wit 'n the tube, current conducting mea mounted on said core, said core having a ntral longitudinal bore at the end thereo a rod having one end inserted into the bore, said core having a radial opening therein adjacent the longitudinal bore, a screw passing through the radial opening and threaded into the rod, said opening be' ofappreciably larger diameter than the diameter of the screw thereby permitting a limited free sidewise movement of the screw in the radial hole and a similar longitudinal movement of the rod,

said current conducting means being connected to said rod through said screw, and means for supporting the other end of the rod within the tube'thereby supporting the core. v

7. A resistance unit comprising an insulating sleeve having a cap secured upon one end thereof, a ferrule secured on the other end, a central rod of ceramic insulation, metallic mounts for the ends of the rod, one of said mounts being secured to the.- cap, a spider connecting the other mount inside the ferrule, a wire resistor disposed on the rod and connected to said mounts, said mounts including means cooperating with the rod to provide I 8. A resistanceunlt compr sing an mounts being secured to the cap, a spider connectin the other mount inside the ferrule, a wire reslstor disposed on the rod and connected to said mounts, said mounts including 5 means providingyielding mechanical connections between t e rod and the mounts, and providing electrical connections between the resistor and the mounts, and a closure for the end of the ferrule.

.1 9. In combination, a rod of insulating material, metallic mounts non-rotatably secured on the ends of said rod, a wire resistor wound upon the rod, said mounts including means cooperating with the rod to provide yielding connections therebetween, an enclosing casing of insulation having metallic terminals thereupon forming closures for the casing, one of said mounts being connected rigidly, mechanically and electrically to one 29 of said terminals, the other of said mounts being connected to another terminal electrically and supported radially to permit endwise expansion and contraction of the rod.

10. In combination, a rod of insulating material, metallic mounts non-rotatably secured on the ends of said rod, a wire resistor wound upon the rod, said mounts including means providing yielding mechanical connections between the rod and the mounts, and providing electrical connections between the resistor and the mounts, an enclosing casing of insulation having metallic terminals thereupon forming closures for the casing, one of said mounts being connected rigidly, mechanically and electrically to one of said terminals,

' the other of said mounts being connected to another terminal electrically and supported radiallyto permit endwise expansion and contraction of the rod.

In witness whereof, I hereunto subscribe my name this 24thday of January, 1928.

, NICHOLAS J. CONRAD. 

